Map Projections

Equator: 435.767223 Decimal Degrees
Southern Graticule 143.839123 Decimal Degrees
Northern Graticule: 188.049757 Decimal Degrees

Geodesic: 100.364186 Decimal Degrees
Great Elliptic: 100.364268 Decimal Degrees
Loxodrome: 117.061322 Decimal Degrees

Map Projections

A map projection transforms the 3-d globe into a 2-d surface.  A projection cannot preserve all of the features of the globe, such as distance, direction, area, and shape because it takes spherical coordinates (x,y, and z) and transforms them into 2-d space (x, y).  Consequently, some error/distortion is introduced and each map projection contains certain errors. This is why maps are typically named after the features they do preserve - such as equidistant or equal area.

Map projections are critical to GIS projects. You need to choose the right projection depending on your research in order to achieve accurate results. For example, if your study focuses on the distance between features, cities, etc, it is critical that you use an equidistant map, such as azimuthal equidistant or equidistant conic (first two projections). These maps preserve distance and will give you accurate results. If you chose a projection that does not preserve distance, such as Mollweide or Mercator, your results would be inaccurate and would impact all your research and data information. A projection is the most basic, fundamental component of any GIS project and shapes the results.

The first two projections preserve distance from some standard point or line. I chose World Azimuthal Equidistant and Sphere Equidistant Conic. With the former, distances and directions to all places are true only from the center point of projection. Distances are accurate between points along straight lines through the center; all other distances are inaccurate. Distortion of areas and shapes increases the further away you get from the center. For example, in the Azimuthal Equidistant map, Antarctica is tiny and not at all true to its size. 


The next two projections preserve area which means that the images on the map are proportional to the area of the landforms they represent. I chose the Cylindrical Equal Area and Mollweide. These equal area maps are useful for calculating the area of countries, continents, etc. They give you an accurate representation (area) of the world. If you were to use an equal area map to figure out something else, such as distance, it would be inaccurate, which is clear from different distances between Kabul and Washington D.C. 


The last two projections are examples of conformal maps, which preserve shape by preserving the angles of feature boundaries, such as countries or continents. By preserving the angles, the area within the features is distorted. For example, in the first conformal map (Mercator projection) the shape of Greenland is accurate but is dramatically larger than it actually is. If you referenced the equal area maps, you would see that Greenland is actually the size of Mexico.Additionally, conformal projections do not preserve the shapes of features that are close the poles (ex. Antarctica). Conformal projections are useful for navigating angles/traveling (via boat/airplane). 


Clearly, the potential of map projections is huge. There's a map projection for your spatial needs, whatever they are. The only thing to be weary of is the sensible and knowledgeable selection of the map projection that will give you accurate results. This requires some knowledge about map projections, including the different types and which features they preserve.